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541.
Talu E Lozano MM Powell RL Dayton PA Longo ML 《Langmuir : the ACS journal of surfaces and colloids》2006,22(23):9487-9490
In this letter, the long-term stabilization of monodisperse microbubbles produced by flow focusing is demonstrated using lipid encapsulation. Fluorescence microscopy, high-speed camera imaging, and particle size analysis were used to investigate the roles of lipid phase behavior, dissolution, Ostwald ripening, and coalescence in the stability of microbubbles formed by flow focusing. It was found that these behaviors were controlled through compositional changes with respect to lipid, emulsifier, and viscosity agents. Microbubbles coated with lipid and PEG emulsifier in a viscous solution were found to contain an extremely narrow size distribution (diameter(av) = 51 microm, standard deviation = 4 microm), which was maintained for up to several months. 相似文献
542.
We report on a fluorescence microscopy study of the monolayer collapse and shedding behavior due to shell compression during the dissolution of air-filled, lipid-coated microbubbles in degassed media. The monolayer shell was comprised of saturated diacyl phosphatidylcholine (C12:0 to C22:0) and an emulsifier, poly(ethylene glycol)-40 stearate. The morphologies of monolayer collapse structures and shed particles were monitored as a function of phospholipid acyl chain length (n) and temperature. The two components formed a single miscible phase when the phospholipid was near or above its main phase transition temperature, and collapse occurred via suboptical particles to vesicles (both were shed) and tubes as chain length increased. Conversely, two-phase coexistence was observed when the lipid was below its main phase transition temperature. For these bubbles, a transition from primary collapse to secondary collapse was observed. Primary collapse was observed as a loss of expanded phase due to vesiculation. Secondary collapse involved the rapid propagation of monolayer folds and simultaneous deformation. For very rigid monolayers, we observed substantial surface buckling with simultaneous nucleation and growth of folds. The folds merged at a single point or region, providing a conduit for the entire excess lipid to shed in a single event, and the bubble smoothed and became more spherical. These results are discussed in the context of general binary phospholipid collapse behavior, microbubble dissolution behavior, medical applications, and the dissolution behavior of natural microbubbles. 相似文献
543.
Orlandi MO Leite ER Aguiar R Bettini J Longo E 《The journal of physical chemistry. B》2006,110(13):6621-6625
This article reports on the growth of SnO nanobelts and dendrites by a carbothermal reduction process. The materials were synthesized in a sealed tube furnace at 1210 degrees C and at 1260 degrees C for 2 h, in a dynamic nitrogen atmosphere of 40 sccm. After synthesis, gray-black materials were collected downstream in the tube and the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The results showed that the gray-black materials were composed of nanobelts, which grew in the [110] direction of the orthorhombic structure of SnO. Some of the belts also presented dendritic growth. The dendrites grew in the (110) planes of the SnO structure, and no defects were observed at the junction between the nanobelts and the dendrites. A self-catalytic vapor-liquid-solid (VLS) process was proposed to explain the growth of the SnO nanobelts and dendrites. 相似文献
544.
Paolo Camassa Roberto Longo Yoh Tanimoto Mihály Weiner 《Communications in Mathematical Physics》2012,309(3):703-735
We analyze the set of locally normal KMS states w.r.t. the translation group for a local conformal net A{{\mathcal A}} of von Neumann algebras on
\mathbb R{\mathbb R} . In this first part, we focus on the completely rational net A{{\mathcal A}} . Our main result here states that, if A{{\mathcal{A}}} is completely rational, there exists exactly one locally normal KMS state j{\varphi} . Moreover, j{\varphi} is canonically constructed by a geometric procedure. A crucial r?le is played by the analysis of the “thermal completion
net” associated with a locally normal KMS state. A similar uniqueness result holds for KMS states of two-dimensional local
conformal nets w.r.t. the time-translation one-parameter group. 相似文献
545.
Paulo G. Mendes Mario L. Moreira Sergio M. Tebcherani Marcelo O. Orlandi J. Andrés Maximu S. Li Nora Diaz-Mora José A. Varela Elson Longo 《Journal of nanoparticle research》2012,14(3):750
The exploration of novel synthetic methodologies that control both size and shape of functional nanostructure opens new avenues
for the functional application of nanomaterials. Here, we report a new and versatile approach to synthesize SnO2 nanocrystals (rutile-type structure) using microwave-assisted hydrothermal method. Broad peaks in the X-ray diffraction spectra
indicate the nanosized nature of the samples which were indexed as a pure cassiterite tetragonal phase. Chemically and physically
adsorbed water was estimated by TGA data and FT-Raman spectra to account for a new broad peak around 560 cm−1 which is related to defective surface modes. In addition, the spherical-like morphology and low dispersed distribution size
around 3–5 nm were investigated by HR-TEM and FE-SEM microscopies. Room temperature PL emission presents two broad bands at
438 and 764 nm, indicating the existence of different recombination centers. When the size of the nanospheres decreases, the
relative intensity of 513 nm emission increases and the 393 nm one decreases. UV–Visible spectra show substantial changes
in the optical absorbance of crystalline SnO2 nanoparticles while the existence of a small tail points out the presence of localized levels inside the forbidden band gap
and supplies the necessary condition for the PL emission. 相似文献
546.
Fabrizio Bardelli Germana Barone Vincenza Crupi Francesca Longo Giacomo Maisano Domenico Majolino Paolo Mazzoleni Valentina Venuti 《Journal of synchrotron radiation》2012,19(5):782-788
The present work reports a detailed investigation on the speciation of iron in the pigments of decorated pottery fragments of cultural heritage relevance. The fragments come from the Gioiosa Guardia archaeological site in the area of the `Strait of Messina' (Sicily, Southern Italy), and date back to VI–V century BC. The purpose of this study is to characterize the main pigmenting agents responsible for the dark‐red coloration of the specimens using non‐destructive analytical techniques such as synchrotron radiation X‐ray absorption spectroscopy (SR‐XAS), a well established technique for cultural heritage and environmental subjects. Absorption spectra were collected at the Fe K‐edge on the Italian beamline for absorption and diffraction (BM8‐GILDA) at the European Synchrotron Radiation Facility in Grenoble (France). In order to determine the speciation of Fe in the samples, principal component analysis and least‐squares fitting procedures were applied to the near‐edge part of the absorption spectra (XANES). Details on the local structure around the Fe sites were obtained by analyzing the extended part of the spectra (EXAFS). Furthermore, an accurate determination of the average Fe oxidation state was carried out through analysis of the pre‐edge peaks of the absorption spectra. Samples resulted composed of an admixture of Fe2O3 (hematite or maghemite) and magnetite (Fe3O4), occurring in different relative abundance in the dark‐ and light‐colored areas of the specimens. The results obtained are complementary to information previously obtained by means of instrumental neutron activation analysis, Fourier transform infrared absorbance and time‐of‐flight neutron diffraction. 相似文献
547.
Ferruccio Casabuona Antonio Longo Angelo Crugnola Paolo Lombardi 《Tetrahedron letters》1981,22(41):4145-4148
The total synthesis of chiral “4,7-lactam” has been accomplished starting from 4-acetoxyazetidinone. An independent route from methyl penicillanate has been used to test the efficiency of the foregoing synthesis. 相似文献
548.
549.
L.E.B. Soledade E. Longo E.R. Leite F.M. Pontes F. Lanciotti Jr. C.E.M. Campos P.S. Pizani J.A. Varela 《Applied Physics A: Materials Science & Processing》2002,75(5):629-632
Room-temperature photoluminescence (PL) was observed in undoped and 2 mol % Cr-, Al- and Y-doped amorphous SrTiO3 thin films. Doping increased the PL, and in the case of Cr significantly reduced the associated PL wavelength. The optical
bandgaps, calculated by means of UV–vis absorption spectra, increased with crystallinity and decreased with the doping level.
It was considered that yttrium and aluminum substituted Sr2+, whereas chromium replaced Ti4+. It is believed that luminescence centers are oxygen-deficient BO6 complexes, or the same centers with some other defects, such as oxygen or strontium vacancies, or BO6 complexes with some other defects placed in their neighborhood. The character of excitation and the competition for negatively
charged non-bridging oxygen (NBO) among numerous types of BO6 defect complexes in doped SrTiO3 results in various broadband luminescence peak positions. The results herein reported are an indicative that amorphous titanates
are sensitive to doping, which is important for the control of the electro-optic properties of these materials. The probable
incorporation of Cr into the Ti site suggests that the existence of a double network former can lead to materials displaying
a more intense photoluminescence.
Received: 20 November 2001 / Accepted: 22 November 2001 / Published online: 27 March 2002 相似文献
550.
Sergio De Munari Giuseppe Marazzi Angelo Forgione Antonio Longo Paolo Lombardi 《Tetrahedron letters》1980,21(23):2273-2276
The assignment of the S-(+), R-(?) absolute configuration of Indoprofene, an analgesic and anti-inflammatory drug, has been made via an NMR configurational correlation of diastereoisomeric phenylethylamides with the aid of Eu(fod)3. 相似文献